Precision Mag (PMI) although I don't think are made any longer. You can still find some new for sale though. I had a 20 rd one and it worked fine. I have heard PMI made mags for Ruger but I cannot confirm this.Some say promag metal are ok. They are hit or miss in my experience. Your mileage may vary. For high cap I would stick with 20 round ruger factory mags.